This invention relates to a plastic laminate having a polyamide resin surface layer, a fluororesin surface layer and an intermediate layer of a resin blend. In the laminate the both surface layers are welded to the intermediate layer. The plastic laminate can be produced in sheet form or tubular form.
In this specification the term "polyamide" always refers to an aliphatic polyamide that is called nylon. Polyamide resins have well balanced properties and are excellent particularly in mechanical strength, toughness, wear and abrasion resistance, moldability and workability. Accordingly polyamide resins are largely used as molding materials for automotive parts, electric parts, general machine parts, etc. Besides, flexible nylon resins which are below about 5000 kgf/cm.sup.2 in tensile modulus of elasticity are used for pipes and hoses in automated machines, industrial robots, automobiles, etc.
In expanding the use of polyamide resins there is a problem that polyamide resins are rather inferior in acid resistance and methanol resistance. For example, in the case of an automotive fuel hose using a flexible nylon resin such as nylon 11 or nylon 12 the hose is short in service life if sour gasoline frequently flows in the hose, and the nylon resin hose can hardly be used for methanol or a mixed fuel containing methanol because the nylon resin is easily swelled by methanol.
Fluororesins are excellent in chemical resistance and weather resistance, but fluororesins are generally costly. Therefore, various attempts have been made to produce a plastic laminate having a polyamide layer and a fluororesin layer. However, it is very difficult and almost impracticable to produce such a laminate by welding the two kinds of resin layers because fluororesins are generally poor in compatibility with different resins. Therefore it is usual to accomplish the aimed lamination by using an adhesive and making a pretreatment of a surface of the fluororesin layer such as a corona discharge treatment or a chemical etching treatment, and hence the lamination process complicates and entails troublesome operations especially in the case of producing a laminated pipe or hose.